feat(apple): brand accent color (#6656F2) via the asset catalog

AccentColor color set + ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME on all four app
configurations — the platform-sanctioned global tint, so the host-card icons, prominent
buttons, toggles, pickers and links all carry the brand violet on macOS and iOS without
any per-view styling.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/apple/App/Assets.xcassets/AccentColor.colorset/Contents.json

@@ -0,0 +1,20 @@
+{
+  "colors" : [
+    {
+      "color" : {
+        "color-space" : "srgb",
+        "components" : {
+          "alpha" : "1.000",
+          "blue" : "0xF2",
+          "green" : "0x56",
+          "red" : "0x66"
+        }
+      },
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

clients/apple/Punktfunk.xcodeproj/project.pbxproj

@@ -298,6 +298,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ASSETCATALOG_COMPILER_APPICON_NAME = punktfunk_Logo;
+				ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME = AccentColor;
 				CODE_SIGN_IDENTITY = "-";
 				"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "Apple Development";
 				CODE_SIGN_STYLE = Automatic;
@@ -330,6 +331,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ASSETCATALOG_COMPILER_APPICON_NAME = punktfunk_Logo;
+				ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME = AccentColor;
 				CODE_SIGN_IDENTITY = "-";
 				"CODE_SIGN_IDENTITY[sdk=iphoneos*]" = "Apple Development";
 				CODE_SIGN_STYLE = Automatic;
@@ -362,6 +364,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ASSETCATALOG_COMPILER_APPICON_NAME = punktfunk_Logo;
+				ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME = AccentColor;
 				CODE_SIGN_STYLE = Automatic;
 				CURRENT_PROJECT_VERSION = 1;
 				DEVELOPMENT_TEAM = F4H37KF6WC;
@@ -398,6 +401,7 @@
 			isa = XCBuildConfiguration;
 			buildSettings = {
 				ASSETCATALOG_COMPILER_APPICON_NAME = punktfunk_Logo;
+				ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME = AccentColor;
 				CODE_SIGN_STYLE = Automatic;
 				CURRENT_PROJECT_VERSION = 1;
 				DEVELOPMENT_TEAM = F4H37KF6WC;